1. Field of the Invention
The invention is directed to a bearing used for coupling a straw walker pan to a straw walker crank.
2. Description of the Prior Art
Agricultural combines process a harvested crop by first threshing the harvested crop, then separating the threshed crop, and finally cleaning the chaff from the separated grain. In conventional combines the separating function is accomplished by straw walkers. Straw walkers expand and agitate the threshed crop mat so that grain is free to fall through the crop mat to the cleaning system. The straw walkers comprise a series of pans arranged axially within the combine. These pans are moved up and down, and forward and backward, by transverse straw walker cranks located on the underside of the pans.
Presently, straw walker pans are coupled to the cranks by wooden bearing blocks. The straw walker cranks are provided with a series of throws that correspond to a series of separate straw walker pans. Crimped centering rings are mounted to each crank. Two wooden blocks each having a semi-cylindrical recess for half the crank and a corresponding recesses for centering rings are sandwiched around the straw walker crank and bolted to one another. The centering rings prevent the bearing from moving transversely along the crank.
Because of the manufacturing process used in manufacturing straw walker cranks the outer diameter of the throws of some cranks maybe greater than desired. When wooden bearings designed for conventional cranks are mounted to large diameter cranks the wooden bearings are tight and cause excessive wear of the cranks and bearing. In the past cardboard spacers were inserted between the wooden bearing portions. After approximately five hundred hours of operation the spacers were removed and the bearing retightened.
Straw walker bearings work in a harsh pressurized dust infested environment. Wooden bearings shrink and swell according to the moisture in the air. As such the bearings run tight or loose in accordance with the humidity. The wood can also become embedded with dirt and grit which acts as an abrasive to wear the steel crank. In addition, the crimped steel centering rings may become loose allowing the walker pans to collide with one another and crimped centering rings are difficult to repair.